There is evidence that lower brainstem auditory pathways perform important initial steps in analyzing the temporal pattern of sound. The long-term goal of the proposed research is to understand the unique contribution of each lower brainstem auditory pathway to the process of analysis, transformation and integration that results in temporal pattern perception. The specific aims of the proposed project focus on the broad question of how intrinsic properties of auditory neurons interact with synaptic inputs to shape sound-evoked responses. The specific aims are 1) To elucidate the roles of ascending input pathways in shaping sound-evoked responses of neurons in the nuclei of the lateral lemniscus (NLL); 2) To characterize the distribution and functional roles of voltage-gated ion channel in the NLL; 3) To correlate sound -evoked response patterns with neurons' morphology and ion channel distributions; and 4) To characterize the contribution of the NLL to shaping sound-evoked responses of the inferior colliculus (IC) neurons. Responses of NLL and IC neurons to sound will be recorded extracellularly and intracellularly. Stimuli will be pure tones of sound with simple temporal patterns. To examine the role of lower brainstem nuclei in shaping the responses of NLL or IC neurons, activity of inputs will be selectively and reversibly blocked. In addition, blockers of specific neurontransmitters or voltage-gated ion channels will be applied locallly to the neuron from which we are recording. It is likely that the results of these experiments will be widely applicable to mammalian hearing. All animals that hear must analyze the temporal patterns of sound; for humans, temporal patterns are the basis of both music and speech perception. Understanding how temporal patterns are analyzed in the auditory system could ultimately have implications for diagnosis and treatment of hearing and language disorders, ad could provide insight into general mechanisms that operate in all neural systems with patterns of time-varying information.